Panel self refresh (hereinafter, also “PSR”) is known as a technique for transmitting an image to a display panel. PSR is processing in which a frame (an image) transmitted from a host apparatus to a display panel is held in a frame memory and, in a case where a next frame transmitted from the host apparatus is the same as that in the frame memory, the host apparatus is stopped and the frame in the frame memory is transmitted to the display panel. The use of the frame memory can reduce power consumption by transmission of the frame by the host apparatus to the display panel.
Further, in PSR, a compressed (coded) frame is held in the frame memory for reducing the cost of the frame memory.
However, there is a problem that in a case where a compression ratio is not sufficient, the frame cannot be stored in the frame memory because of the limited capacity of the frame memory and PSR cannot be started. On the other hand, in a case where the frame is compressed at a high compression ratio so that the frame can be stored in the frame memory, a distortion of an image (an error from an original image, hereinafter, also “compression distortion”) is caused by compression and deteriorates image quality.
Therefore, it is demanded to achieve both the reduction in the power consumption and the improvement of the image quality simultaneously.